[R] Difference between times

[Prof Brian Ripley]

On 18/04/2014 19:46, Rui Barradas wrote:
> Hello,
>
> The reason why is that you've misspelled CET (not CEST)

Neither CET nor CEST are portable time-zone names.  We have not been 
given the 'at a minimum' information required by the posting guide, so 
please read ?Sys.timezone on your system.


>
>  > dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz =
> "CEST")
> Warning messages:
> 1: In strptime(x, format, tz = tz) : unknown timezone 'CEST'
> 2: In as.POSIXct.POSIXlt(as.POSIXlt(x, tz, ...), tz, ...) :
>    unknown timezone 'CEST'
>  > dt2 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz =
> "GMT")
>  > dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz =
> "CET")
>  > dt1-dt2
> Time difference of -2 hours
>
>
> Hope this helps,
>
> Rui Barradas
>
> Em 18-04-2014 17:13, Nicola Sturaro Sommacal escreveu:
>> Hi.
>>
>> I am new to POSIX and I'd like to understand the reason of this
>> difference.
>>
>> dt1 = as.POSIXct("2014-03-29 09.00", format="%Y-%m-%d %H.%M")
>> dt2 = as.POSIXct("2014-03-30 09.00", format="%Y-%m-%d %H.%M")
>> dt2-dt1
>>
>>> dt1[1] "2014-03-29 09:00:00 CET"> dt2[1] "2014-03-30 09:00:00 CEST">
>>> dt2-dt1
>>
>> Time difference of 23 hours
>>
>> This is right, because on Mar 31 at 2 PM we jump directly to 3PM, DST.
>>
>> On the contrary, I don't understand the following:
>>
>> dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz =
>> "CEST")
>> dt2 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = "GMT")
>>
>>> dt1[1] "2014-04-18 09:00:00 CEST"> dt2[1] "2014-04-18 09:00:00 GMT">
>>> dt1-dt2Time difference of 0 secs
>>
>>
>> I should expected a time difference of 2 hours, as CEST is GMT+2.
>>
>> Anyone can help me?
>>
>> Thank you,
>> Nicola
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595